# Calories from Macros Calculator

URL: https://speedycalculator.com/calculators/food/food-calories/
Last updated: 2026-10-25

> This calculator works out the calories in a food or meal from its grams of protein, carbohydrate, fat and alcohol, using the Atwater factors of 4, 4, 9 and 7 kcal per gram.

## Inputs

- Protein (g)
- Carbohydrate (g)
- Fat (g)
- Alcohol (g)

## Results

- Calories
- Kilojoules
- From protein
- From carbs
- From fat

## Formula

```
kcal = 4 × protein + 4 × carbs + 9 × fat + 7 × alcohol
```

## Explanation

Nutrition labels use these factors, so you can check a label or estimate calories for a homemade dish.

### How to use the Calories from Macros Calculator

- **Protein**
- **Carbohydrate**
- **Fat**
- **Alcohol**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Multiply each macronutrient by its energy factor and add them.

### Inputs explained

FieldWhat to enterProteinIn gCarbohydrateIn gFatIn gAlcoholIn g

### What each result means

- **Calories** = 4×[Protein] + 4×[Carbohydrate] + 9×[Fat] + 7×[Alcohol]
- **Kilojoules** = [Calories]×4.184
- **From protein** = 4×[Protein]÷[Calories]×100
- **From carbs** = 4×[Carbohydrate]÷[Calories]×100
- **From fat** = 9×[Fat]÷[Calories]×100

### Example values

How the main result changes when **Protein** changes and everything else stays at the example values above:

Protein (g)Calories (kcal)12.534518.753702539531.2542037.544550495

## Worked example

Inputs — Protein: 25 g; Carbohydrate: 40 g; Fat: 15 g; Alcohol: 0 g.

Results — **Calories = 395 kcal**; Kilojoules = 1,653 kJ; From protein = 25.3 %; From carbs = 40.5 %; From fat = 34.2 %.

## FAQ

**Does fibre count as carbohydrate?**
On U.S. labels it is included in total carbs; it provides about 2 kcal/g.

**Why might a label differ slightly?**
Labels round values and may use specific factors for some foods.

**What formula does the Calories from Macros Calculator use?**
kcal = 4 × protein + 4 × carbs + 9 × fat + 7 × alcohol.


## Sources

- [USDA FoodData Central](https://fdc.nal.usda.gov/)